Previous studies of the neural mechanisms of decision-making have neglected an essential factor- that real world decisions almost always involve outcomes occurring at different times. Generally, delayed outcomes are valued less than immediate outcomes, a process called temporal discounting. Decision-making deficits seen in drug addiction, frontal lobe damage and psychiatric disease may centrally result from altered temporal discounting. This project investigates the neural mechanisms of temporal discounting in humans, by measuring neural activity with fMRI while subjects decide between monetary gains (Aim 1) or losses (Aim 2) that occur at different times. We will test whether any regions represent the subjective value of outcomes, discounted for the delay to their occurrence, and further how any such representations (neurometric discount functions) are related to psychophysical discount functions calculated from subjects' choices. Ultimately, a mature model of how the brain makes decisions must explain how different outcomes are valued given that they rarely occur at the same time. By aiming to establish a quantitative understanding of the neural processes involved in temporal discounting, this project hopes to build towards that goal.